The Siege of Skyhold (Mage Errant #5)

The Havath Dominion is marching to war.

Humiliated in the ruins of Imperial Ithos, the Exile Splinter stolen from their grasp by the ancient sphinx Kanderon Crux, Havath's Duarchs have assembled an army that dwarfs the entire population of Skyhold. Led by their Great Powers, monsters and mages individually capable of leveling a city, they pose a threat that even Kanderon, one of the mightiest of Great Powers, and her equally monstrous allies might be unable to stop.

As the Havathi forces push closer and closer to Skyhold, Hugh and his friends train relentlessly, hoping to make a difference in the oncoming siege. While they venture into dangerous realms of untested experimental magic, though, they're already caught up in currents far beyond their control.

Once you're a pawn in the games of the Great Powers, there's no escape.